It is calculated,
however, to seed the levees as well as the check bottoms, and to run the
mowers across the levees, thus leaving no waste land and mowing across
the whole field and not between the levees as you propose. For that
purpose these levees are made low, not over a foot in height,
calculating that they will settle to about six or eight inches, which is
sufficient to hold the water and direct its flow gently down the slope.
There is, however, a limit to the distance over which water can be
evenly distributed in this way, the difference being dependent upon the
character of the soil, slope, etc. A length of nine hundred feet is
sometimes found too great for an even distribution, and, for this
reason, supply ditches at shorter intervals are introduced.
Unirrigated Alfalfa.
In what part of the State does alfalfa grow best without irrigation?
Obviously the parts which have the greatest rainfall in connection with
retentive soil and plenty of summer heat. Alfalfa grows best without
irrigation on "sub-irrigated" land where the ground water is
sufficiently deep to allow a deep rooting of the plant in free soil and
yet not too far down to be readily reached by the deep-running roots.
Good results can be obtained with anywhere from four to ten or twelve
feet of soil above water. On shallower soils the plant is apt to be
short-lived through root troubles.
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